1. Field of the Invention
The present invention relates generally to a distributive type fuel injection apparatus for a multi-cylinder Disel engine and, more particularly, to an injection apparatus which fails to inject fuel into specific cylinders during conditions of engine idle at no load.
2. Description of the Prior Art
The distributive type fuel injection apparatus of the general type has been well known, for example, from Japanese Utility Model Application No. 50736/1979 and the like. Such apparatus is shown in FIG. 1 wherein a rotor 9 having vanes 71 is housed internally of the end walls on a casing 4 to form a feed pump 37. The rotor 9 has its shaft 1 synchronously rotated by the engine and a plunger 52 is coupled to the inner end of the shaft 1 by an Oldham's coupling. Encircling the outer periphery of the shaft 1 is a cylindrical holder 29 that is fixed axially but may be rotated slightly. The holder 29 supports cam followers 11 of the same number as the engine's power cylinders by means of circumferentially spaced pins and is controlled in rotation by an injection timing control device 8 engaged through a lever 28.
Coupled to a plunger 52 is a cam disc 27 that is biased by springs (not shown) engaging the cam followers 11, and is reciprocated as the shaft 1 rotates. A cylindrical body 30 is fitted in and secured to an end wall of the casing 4 and is closed by a threaded plug 17. Mounted for rotary and reciprocating movement within the cylindrical body 30 is a fuel distribution plunger that defines therewith a pressure chamber 16. In the peripheral wall of the body 30 is arranged a suction port 15 and discharge ports 19 of the same number as the engine's power cylinders and axially spaced relative to each other. The suction port 15 is connected to a discharge port of the feed pump 37 via the interior of the casing 4. Disposed in circumferentially equally spaced relationship, each of the discharge ports 19 is connected by a valve 6 to an injection valve of a different power cylinder of the engine.
Provided in the outer peripheral surface of the plunger 52 are suction passages 18 of the same number as that of the power cylinders and periodically connecting the suction port 15 and the pressure chamber 16. Also, the plunger 52 is provided with an axial passage 22, one end of which communicates with the pressure chamber 16. A central portion of the passage 22 communicates with a radial discharge passage 20 that sequentially registers with the individual discharge ports 19. The opposite end of the passage 22 periodically communicates with the fuel reservoir formed internally of the casing 4 via a radially extending overflow passage 21.
A control sleeve valve 24 for opening and closing the overflow passage 21 is slidably fitted over the plunger 52. Connected to the control valve 24 by a ball point is the lower end of a start lever 33. The start lever 33 together with a tension lever 67 is pivotally mounted by a pivot pin 66 to the casing 4 and both are resiliently connected to each other for relative pivotal movement through a given angle. An upper end of the start lever 33 is biased and engaged with a push rod 64 by the force of a spring 63 extending between the upper end of the tension lever 67 and an accelerating lever 62. Coupled for rotation with the shaft 1 by a gear mechanism 72 are centrifugal weights 61 which separate to force the push rod 64 rightwardly. In this manner, the control sleeve 24 is moved in an axial direction of the plunger 52 by the operation of the accelerating lever 62 to adjust the level of fuel injection and also is moved by the centrifugal weights 61 to restrain variation in the rotation of the engine.
To reduce exhaust gases from an engine of the above-described type, it has been proposed recently that certain specific cylinders be placed in a non-injection condition when the engine is running at idle while extra fuel be injected into the remaining cylinders to thereby maintain no-load running at a relatively high speed. In that way the engine can operate on a lesser number of cylinders providing a reduction in harmful components of exhaust gases. It is an object of the present invention to provide a distributive type fuel injection apparatus which provides that type of operation.